1. Field of the Invention
This invention relates to a mounting for an orthodontic hook or the like that can be applied to the assembly of an arch wire fitted in the arch wire groove of a tooth bracket.
2. Prior Art
Hooks have been secured to arch wires for use as anchoring devices for applying forces to the teeth, such as intermaxillary or intramaxillary springs, elastomeric modules or rubber bands. Usually such hooks have been secured to an arch wire by welding or silver soldering, as described, for example, in Armstrong U.S. Pat. No. 3,508,332, issued April 28, 1970, at column 1, lines 35 and 36. Customarily the hooks are attached to an arch wire by the manufacturer and consequently cannot be placed optimally for each patient. It is difficult for hooks to be attached to an arch wire at locations best suited for a particular patient by or for an orthodontist because great skill is required to weld or solder a hook to an arch wire without such operation inadvertently annealing the arch wire. An arch wire which has become annealed has lost its ability to transmit orthodontic forces effectively to the teeth to which the brackets carrying the arch wire are bonded.
Arch wires are custom-fitted to a particular patient by the orthodontist and after a period of treatment it may be desirable to apply a pull or a torque on an arch wire at a particular location. In such case it is desirable to apply a hook to the fitted arch wire at that particular location but it is difficult to make a good soldered joint to attach such a hook if the parts being soldered are not perfectly clean and dry. Cleanliness is difficult to insure for an arch wire that has been in a mouth for any appreciable period of time. A dirty arch wire will require heating to a higher temperature in the hook-attaching operation which increases the risk of annealing the arch wire.
If a poor welded or soldered joint is made, the hook can be pulled from the arch wire because it is subjected to considerable stress by the orthodontic treatment force. If the arch wire is inadvertently annealed as a result of the hook-attaching operation, it may break or bend and lose the resiliency required to transmit orthodontic forces effectively between the teeth to which it is attached by tooth brackets for moving such teeth. On the other hand, if the hook is securely attached to the arch wire, it is difficult to remove the hook at the end of the treatment requiring application of force to a hook, or when it is necessary to relocate the hook, and the arch wire may be impaired or damaged excessively by such removing operation.
During the progress of orthodontic treatment it may be desirable to replace the arch wire with an arch wire of different cross-sectional size and/or shape. Each time the arch wire is changed a new set of hooks is required. Also, depending on the progress of the orthodontic treatment, it may be desirable to apply force to arch wire hooks at different times. Frequently, hooks interfere with the adjustment of an arch wire to accomplish a particular treatment and it is therefore undesirable to have hooks on an arch wire when they are not being used.
Alternatively, hooks have been mounted on caps engageable with orthodontic brackets, as described in Johnson U.S. Pat. No. 3,391,461, issued July 9, 1968, at column 2, lines 24 and 25. A principal difficulty with such a hook mounting is that it is necessary to hold the cap in place to restrain sliding of it relative to the tooth bracket by bending retaining tabs to engage the bracket, which may require that stress be exerted on the tooth bracket that is uncomfortable or even distressing to the patient. If the cap is to be removed, the tabs must be unbent which, again, can produce an undesirable stress on the tooth bracket.
The Waldman U.S. Pat. No. 3,158,934, issued Dec. 1, 1964, shows in FIG. 10 an orthodontic appliance for attachment to an arch wire having two hooks 32 to which springs or rubber bands, presumably, may be attached. Such appliance, however, has a slot 22 positioned to receive the arch wire 14 when the arch wire is parallel to the rear wall 20 forming the slot bottom, as shown in FIG. 2. The appliance is secured to the arch wire by tightening a very small set screw such as 19 in FIG. 1 or 119 in FIG. 2. Such an appliance is anchored directly to the arch wire and is not engaged with a tooth bracket.